Add snapshot and dump methods

Signed-off-by: p4u <p4u@dabax.net>

tree/README.md

@@ -19,4 +19,4 @@ Example of usage:
 
 #### To-Do
 
-+ Add export/import methods
+Avoid duplicates on dump/snapshot

tree/tree.go

@@ -1,36 +1,45 @@
 package tree
 
 import (
-  "github.com/vocdoni/go-iden3/db"
-  "github.com/vocdoni/go-iden3/merkletree"
-  mkcore "github.com/vocdoni/go-iden3/core"
-  common3 "github.com/vocdoni/go-iden3/common"
-  "os/user"
+	"errors"
+	"fmt"
+	"os/user"
+	"strings"
+	"time"
+
+	common3 "github.com/vocdoni/go-iden3/common"
+	mkcore "github.com/vocdoni/go-iden3/core"
+	"github.com/vocdoni/go-iden3/db"
+	"github.com/vocdoni/go-iden3/merkletree"
 )
 
 type Tree struct {
-    Namespace string
-    Storage string
-    Tree *merkletree.MerkleTree
+	Namespace string
+	Storage   string
+	Tree      *merkletree.MerkleTree
+	DbStorage *db.LevelDbStorage
 }
 
 func (t *Tree) Init() error {
-  if len(t.Storage) < 1 {
-    usr, err := user.Current()
-    if err == nil {
-      t.Storage = usr.HomeDir + "/.dvote/Tree"
-    } else { t.Storage = "./dvoteTree" }
-  }
-  mtdb, err := db.NewLevelDbStorage(t.Storage, false)
+	if len(t.Storage) < 1 {
+		usr, err := user.Current()
+		if err == nil {
+			t.Storage = usr.HomeDir + "/.dvote/Tree"
+		} else {
+			t.Storage = "./dvoteTree"
+		}
+	}
+	mtdb, err := db.NewLevelDbStorage(t.Storage, false)
 	if err != nil {
-    return err
+		return err
 	}
 	mt, err := merkletree.New(mtdb, 140)
 	if err != nil {
-	  return err
+		return err
 	}
-  t.Tree = mt
-  return nil
+	t.DbStorage = mtdb
+	t.Tree = mt
+	return nil
 }
 
 func (t *Tree) Close() {
@@ -38,29 +47,72 @@ func (t *Tree) Close() {
 }
 
 func (t *Tree) AddClaim(data []byte) error {
-  claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
-  return t.Tree.Add(claim)
+	isSnapshot := strings.Contains(t.Namespace, "snapshot.")
+	if isSnapshot {
+		return errors.New("No new claims can be added to a Snapshot")
+	}
+	claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
+	return t.Tree.Add(claim)
 }
 
 func (t *Tree) GenProof(data []byte) (string, error) {
-  claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
-  mp, err := t.Tree.GenerateProof(claim.Hi())
-  if err!=nil {
-    return "", err
-  }
-  mpHex := common3.BytesToHex(mp)
-  return mpHex, nil
+	claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
+	mp, err := t.Tree.GenerateProof(claim.Hi())
+	if err != nil {
+		return "", err
+	}
+	mpHex := common3.BytesToHex(mp)
+	return mpHex, nil
 }
 
 func (t *Tree) CheckProof(data []byte, mpHex string) (bool, error) {
-  mp, err := common3.HexToBytes(mpHex)
-  if err != nil {
-    return false, err
-  }
-  claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
-  return merkletree.CheckProof(t.Tree.Root(), mp, claim.Hi(), claim.Ht(), t.Tree.NumLevels()), nil
+	mp, err := common3.HexToBytes(mpHex)
+	if err != nil {
+		return false, err
+	}
+	claim := mkcore.NewGenericClaim(t.Namespace, "default", data, nil)
+	return merkletree.CheckProof(t.Tree.Root(), mp, claim.Hi(), claim.Ht(), t.Tree.NumLevels()), nil
 }
 
-func (t *Tree) GetRoot() (string) {
-  return t.Tree.Root().Hex()
+func (t *Tree) GetRoot() string {
+	return t.Tree.Root().Hex()
+}
+
+/* Dump, Export and Snapshot functions are a bit tricky.
+   Since go-iden3 does not provide the necessary tools. Low level operations must be performed.
+   Once go-iden3 API is mature enough, these functions must be adapted.
+
+   To explore: Values are stored twice in the BD?
+*/
+func (t *Tree) Dump() ([]string, error) {
+	var response []string
+	substorage := t.DbStorage.WithPrefix([]byte(t.Namespace))
+	nsHash := merkletree.HashBytes([]byte(t.Namespace))
+	substorage.Iterate(func(key, value []byte) {
+		nsValue := value[5:37]
+		if fmt.Sprint(nsHash) == fmt.Sprint(nsValue) {
+			response = append(response, string(value[69:]))
+		}
+	})
+	return response, nil
+}
+
+func (t *Tree) Snapshot() (string, error) {
+	substorage := t.DbStorage.WithPrefix([]byte(t.Namespace))
+	nsHash := merkletree.HashBytes([]byte(t.Namespace))
+	currentTime := int64(time.Now().Unix())
+	snapshotNamespace := fmt.Sprintf("snapshot.%s.%d", t.Namespace, currentTime)
+	substorage.Iterate(func(key, value []byte) {
+		nsValue := value[5:37]
+		if fmt.Sprint(nsHash) == fmt.Sprint(nsValue) {
+			data := value[69:]
+			//fmt.Printf(" Adding value: %s\n", data)
+			claim := mkcore.NewGenericClaim(snapshotNamespace, "default", data, nil)
+			err := t.Tree.Add(claim)
+			if err != nil {
+				fmt.Println(err)
+			}
+		}
+	})
+	return snapshotNamespace, nil
 }